The apparatus of the present invention relates generally to material transfer devices and more particularly to an improved method and article of handling substrates within a substrate transport.
The material transferred might include, but not be limited to, semiconductor wafers, such as silicone and gallium arsenide, semiconductor packaging substrates, such as high density interconnects, semiconductor manufacturing processing imaging plates, such as masks or reticles, and large area displayed panels, such as active matrix LCD substrates.
The need for high throughput transport devices which can move a substrate or workpiece between remote locations within a highly confined footprint such as found in the manufacture of wafers or panels or the like used in the semiconductor industry is in high demand. This is because in the process of manufacturing such panels, wafers or the like, the need to move a workpiece from one position to the next not only requires that a high throughput rate be achieved, but also that maximum throughput between component elements of the tool is achieved. In this way, processing time for a given number of substrates can be maximized for a given tool.
Copending U.S. patent application Ser. No. 08/654,334 filed in the name of Hendrickson, filed on May 28, 1996 and entitled A System for Heating or Cooling Wafers and U.S. Pat. No. 5,588,827 entitled A Passive Gas Substrate Thermoconditioning Apparatus and Method, issued on Dec. 31, 1996 to Richard Muka, disclose a substrate transport having a main vacuum transport chamber to which a temperature transfer station is mounted. Thus, it is known in the art to connect an individual substrate thermoconditioning module to a side of the substrate transport outside of the main transport chamber. Also, in copending U.S. patent application Ser. No. 08/891,532 filed under Express Mail No. EM029241165 US and entitled A Substrate Processing Apparatus Having A Substrate Transport with a Front End Extension and an Internal Substrate Buffer, filed on Jul. 11, 1997 in the name of David Beaulie and Michael W. Pippins, now U.S. Pat. No. 5,882,413, discloses a method and apparatus for forming an integrated platform in which a wafer cooler is provided. However, the device disclosed in this patent application has an extended footprint as it uses separate elements, namely, a cooler 36, a buffer, and load locks to effect three different functions for the three separate elements. However, the fabrication and usage of the three elements occupies much needed additional footprint space which otherwise could be used for other process modules and/or cluster tools in the substrate fabrication process.
Accordingly, it is an object of the invention to provide a single substrate load lock with offset cool module and buffer chamber which is capable of transporting substrates from an external environment to a vacuum environment for processing and then back to a factory interface in a manner such that no damage occurs due to thermal shock or nonuniformity in the substrate.
Another object of the invention is to provide a substrate load lock of the aforementioned type wherein the cost of fabrication is reduced by efficiency of the design and construction.
Still a further object of the invention is to provide a substrate load lock of the aforementioned type which is reduced in complexity of drive mechanisms and controls.
It is still a further object of the invention to provide substrate load lock of the aforementioned type which reduces vacuum volume thereby reducing the amount of pumping capability required to maintain adequate vacuum in the system.
Yet still a further object of the invention is to provide a substrate load lock of the aforementioned type wherein the manufacturing time, complexity of construction, alignment in time testing are reduced.
Further still an object of the invention is to provide a substrate load lock of the aforementioned type wherein service and reliability as well as reduced system time throughput are enhanced.
The invention resides in the single substrate load lock with offset cool module and buffer chambers. The load lock is provided as an interface to a substrate handling transport system via a vacuum isolation slot valve. The load lock allows for a single substrate transition from an external environment to the vacuum environment of the transport chamber while a second substrate may reside either in the buffer chamber or the cooling chamber. In either case, with or without a substrate in the buffer or cooling chambers, the load lock is adapted and is configured to provide a throughput mode wherein a substrate is loaded into the load lock from the outside without interfering with a substrate placed either in the buffer chamber or in the cooling chamber.
The invention further relates to a method of handling a substrate in a cluster tool wherein a load lock with a cool down chamber and a buffer chamber is provided and is in selective vacuum communication with a transfer chamber associated with one valve and a second valve associated with an external environment. Thus, the system provides a reduced impact from vacuum to substrates as each is exposed to vacuum when moved from an external environment and vice versa. It is preferred to open the external valve to the external environment only when a substrate is sealed within one of the subchambers by either upward or downward movement of the poppet. In other words, the load lock configuration allows for fast venting only of empty areas where no substrate is disposed, but venting in the sealed subchambers is, rough or staggered, thus avoiding shocking the substrate.
More specifically, the invention resides in a typical sequence whereby a processed substrate is moved into the load lock and onto the holding members of the poppet, the poppet is lowered into subchamber and interior valve is closed. Fast evacuation of the main chamber and subchamber (empty) next begins. Next, cooling in a subchamber may take place. The external environment valve is opened and a new substrate is placed onto the poppet. The poppet is raised. Slow rough evacuation of the subchamber with the new substrate held therein is accomplished. Removal of cooled substrate from the poppet next occurs. The external environment valve is next closed. Fast evacuation of all chambers occurs and the internal valve is opened. The transport apparatus places a processed substrate onto the poppet. The poppet is next lowered. The transport apparatus may pick or place another substrate from the poppet if appropriate, and the internal valve is closed.